12
Safeguard Against Loosening Adhesive coatings

Safeguard Against Loosening - Bossard Group

  • Upload
    others

  • View
    3

  • Download
    0

Embed Size (px)

Citation preview

Page 1: Safeguard Against Loosening - Bossard Group

Safeguard Against LooseningAdhesive coatings

Page 2: Safeguard Against Loosening - Bossard Group

2

“Adhesive coatings create a high level of protection against independent loosening”

Page 3: Safeguard Against Loosening - Bossard Group

3

ADHESIVE COATINGS

Safeguard Against Loosening Adhesive coatings are the most secure preliminary coatings for threaded parts with increased safety requirements.

Threadlocking

Screw connections generally fail due to a loss of preload force. The main cause for this is the loss of the preload force due to independent loosening.

Increased Security

Independent loosening is caused by all kinds of dynamic loads, such as vibrations or temperature changes. Too small of a clamping force and poorly fitting surfaces allow for relative movements, which increase the risk of independent loosening.

These alternating loads lead to short-term fricti-on-free states, which moves the screw relative to the nut. In sum, these tiny movements lead to a screw connection becoming loose.

Independent loosening can be prevented by using suitable screw securing means. Adhesive coatings are one type of securing. These adhesive coatings are always all-around coatings. These act prima-rily as anti-loosening safeguards, which comply with the standard DIN 267 - part 27.

Functional Principle

The coatings consist of the smallest microcapsu-les. When screwing the coated threaded parts into the counter-thread, the microcapsules are destro-yed due to pressure and shear loads.

The curing then starts immediately after assembly. A sufficient functional strength is usually achie-ved after 6 hours. The full curing is achieved after 24 hours.

Adjustment and tightening processes should occur within 5 minutes. Otherwise, the already curing poly merization microstructure can be damaged.

Advantages of Adhesive Coatings

§ Reliable safeguard against loosening § Additionally sealing § Dry, dry to handle and ready for use at any time § No equipment, e.g. dosing devices § Can be used for all materials § For virtually all surfaces § Insensitive to oil and grease after curing § Process reliability § Captive component of the connection element § Simple and safe assembly § Cannot be forgotten

BoltsMikroverkapselter Klebstoff

Page 4: Safeguard Against Loosening - Bossard Group

4

Other UsesIn addition to bonding, sealing against oil, water and fuel also occurs. After the complete curing, the adhesive is a reliable screw lock against independent loosening. Due to the high strength, it is only possible to disconnect the cured connection with difficulty.

Scotch - Grip™ 2353

Scotch - Grip™ 2353 is a microencapsulated screw lock adhesive based on epoxy resin, which was spe-cifically developed for the pre-coating of screws. After the coating, the adhesive remains inactive until it is activated by the capsule breakage when screwed in and then cures at room temperature.

ADHESIVE COATINGS

Product Properties

precote®

precote® offers solutions for securing and sealing. The products developed specifically for the pre-coating of internal and external threads are based on the unique microencapsulation technology, which uses an acrylate system.

The adhesive applied to the thread remains inac-tive prior to use and is dry to handle. The adhesive is first activated when being screwed in, cures at room temperature and offers a reliable lock and/or seal.

Different applications can be realized with three different types. Other products are available by request for customer-specific applications.

precote® 30 (yellow)The thread sealant and medium-strength thread lock. Thread friction coefficient of 0.1 – 0.15. Temperature resistant -60° – 150° C. Easy to disassemble.

precote® 80 (red)Universal, high-strength thread lock. Thread friction coefficient > 0.25. Temperature resistant -60° – 170° C.Also suitable for sealing tasks.

precote® 85 (turquoise)Universal, high-strength thread lock with lowthread friction coefficient of 0.1 – 0.15. Temperature resistant -60° – 150° C.Also suitable for sealing tasks.

Scotch - Grip™ 2353Universal, high-strength thread lock. Thread friction coefficient 0.13 – 0.19.Temperature resistant -30° – 110° C.Also suitable for sealing tasks.

Page 5: Safeguard Against Loosening - Bossard Group

5

Coating Layer and AssemblyCoating layer according to standardUnless defined otherwise, the coating layer and length are applied according to DIN 267-27. Accor-ding to this standard, the coating has a length of about 1x the screw diameter A. The first two to three thread turns are free of the coating to make it easier to screw in.

AssemblyThe assembly of precote® or Scotch – Grip™-co-ated screw occurs mechanically or manually with conventional tools.

The female thread must be free of dust, oil and grease and requires a countersink (90º – 120º) or at least 1.05 x the nominal diameter to prevent a peeling of the coating when screwing in.

PRECOTE / SCOTCH-GRIP 2353

Coating, Construction and Assembly Instructions

-Countersink 90° – 120°,

Ø = 1.05 Ø A

A

B1

BB2

B

Other Useful Information

§ precote® and Scotch – Grip™ are 2-component adhesives and do not require either an air seal or metal ions for curing.

§ precote® and Scotch – Grip™ coatings can also be used in conjunction with plastic screws. However, the achievable breakaway torques with plastic screws is less than with steel screws.

§ Contamination of the coatings is to be avoided, for example from oil.

§ A necessary top coat, for example with an integ-rated lubricant for defined frictional coefficients, should be applied after the precote® coating.

§ For sealing applications, at least 4 thread turns must be coated and installed overlapping to achieve a reliable sealing effect.

Required countersink pursuant to DIN 76 Coating layer and length pursuant to DIN 267-27Length B min 10 mmLength B1 corresponds to approx the diameter of ALength B2 about 2 – 3 thread turns

Page 6: Safeguard Against Loosening - Bossard Group

6

Coating Layer According to Function

To ensure the proper function, it must be ensured that the coating is in the correct position. The stan-dard-compliant coating layer is not always in the correct place for the function.

If the screw with coating is screwed into a blind hole thread too far where the functional coating is not located at the correct location, then the adhe-

Red = coating layer of the functional coatingLocation of the nut = expected location of the nut after assembly

sive distributes across too many thread turns and loses its functionality.

The same applies to screwing on a nut. If screwed beyond the coating here, the functional coating loses its effect.

X

da

X

da

X

OK

Incorrect

OK

OK

External thread

X

da

X

da

X

OK

Incorrect

OK

Incorrect

Coating layer

End position after assembly

X

da

X

da

XX

da

X

da

X

X

da

X

da

X

X

da

X

da

XX

da

X

da

X

X

da

X

da

X

Page 7: Safeguard Against Loosening - Bossard Group

7

Only for monitoring production, according to DIN 267 part 27, or for components that cannot build up any preload force, such as set screws.

1. The tolerance compliance of the nut is checked prior to testing.

2. Assemble the screw into the nut at a maximum of 30rpm making sure that the coating area is completely covered. The maximum screw-in torque MEin is measured.

Test torques without pre-load in Nm for screws (pursuant to DIN 267-27)

ScrewISO 6g

Screw-in torque MIn max. (Nm)

Breakaway torqueMLB min. (Nm)

Loosening torqueMOUT max. (Nm)

M3 0.1 0.2 1.5

M4 0.2 0.4 3.0

M5 0.5 1 6.5

M6 0.8 1.8 10

M8 1.5 4 26

M10 3 10 55

M12 5 16 95

M14 9 22 160

M16 11 35 250

M18 12 40 335

M20 14 45 500

M22 16 65 800

M24 18 90 1050

M27 21 120 1300

M30 25 165 1700

M33 28 210 2400

M36 30 280 3000

M39 35 330 4000

Torque Testing Without Pre-Load

MIn Screw-in torque MLB Breakaway torque MOUT Loosening torque

Torque testing without pre-load to monitor production pursuant to DIN 267, part 27.

3. Allow the adhesive to curing at room tempera-ture (23 +/- 5° C) for 24 hours.

4. Remove the nut at a maximum of 30rpm mea-suring the breakaway torque MLB and the maxi-mum loosening torque MOUT.

Page 8: Safeguard Against Loosening - Bossard Group

8

Test torques with pre-load in Nm for screws (pursuant to DIN 267-27)

ScrewISO 6g 5.6/5.8 8.8/10.9/12.9

Loosening torque MOUT max. (Nm)

RatioMLB / MA

M3 0.6 1.2 1.5

≥ 0.9

M4 1.3 2.8 3.0

M5 2.6 5.5 6.5

M6 4.5 9.5 10

M8 11 23 26

M10 22 46 55

M12 38 79 95

M14 60 125 160

M16 90 195 250

M18 128 280 335

M20 176 390 500

M22 240 530 800

M24 310 670 1050

M27 460 1000 1300

M30 620 1350 1700

M33 825 1850 2400

M36 1100 2350 3000

M39 1400 3000 4000

MA tightening torque MLB breakaway torque MOUT Loosening torque

a) Determined based on a total friction coefficient μges ≈ 0.12 with 90% utilization of the minimum values of the yield strength

(5.6 / 5.8) resp. the yield point (8.8/10.9/12.9) of the lowest strength class.

b) The table values for 5.6 / 5.8 apply for INOX screws according to DIN EN ISO 3506-1 and DIN267-13.

Test tightening torque MA a, b

Torque Testing with Pre-Load

1. The tolerance compliance of the nut is checked prior to testing.

2. Assemble the screw into the nut, bearing against a clean and dry 200 HV washer and sleeve at a maximum of 30rpm per DIN 125 part 2. Tighten to the specified torque making sure that the nut is completely in the coated area.

3. Allow the adhesive to cure at room temperature (23 +/- 5° C) for 24 hours.

4. Remove the nut at a maximum of 30rpm mea-suring the breakaway torque and the loosening torque. The resulting determined ratio MLB / MA may not fall below the value specified in the table under laboratory conditions. The loosening tor-que may not exceed the specified value.

Page 9: Safeguard Against Loosening - Bossard Group

9

Testing the Vibration Strength

Two plates braced against each other with a screw are subjected to a forced vibration (relative movement). Unsecured screws completely loosen within a short period of time.

1. precote® or Scotch-Grip™-coated screws with an adhesive coating have a high clamping force after the usual setting losses, because the screw is adhered and cannot loosen.

2. After a few load changes, uncoated screws lose the pre-load, the connection loosens, the screw loosens and can get lost.

Friction value measurement

When tightening a screw, torque and pre-tension force increase depending on the thread friction value. Depending on the friction value, different pre-tension forces are generated with the same tightening torque.

1. precote® or Scotch-Grip™-coated screws with an adhesive coating are secured against loo-sening. The breakaway torque reaches over 90% of the tightening torque (high-strength). The adhesive residue in the thread generates little friction when loosening.

2. For uncoated screws, the breakaway torque reaches about 70 to 80% of the tightening tor-que. There is no resistance when loosening. The torque and the pre-tension force reach a zero point.

1

2

% pre-tension force

Number of load changes

1 2

Tightening torque

Breakaway torque

Pre-tension force

FQ

FQ

S

Preload force under continuous load (schematic representation)

Torque curve (schematic representation)

Page 10: Safeguard Against Loosening - Bossard Group

10

PROVEN PRODUCTIVITY – A PROMISE TO OUR CUSTOMERS

The strategy for success

From years of cooperation with our customers we know what achieves proven and sustainable impact. We have identified what it takes to streng­then the competitiveness of our customers. There­fore we support our customers in three strategic core areas.

Firstly, when finding optimal product solutions, that is in the evaluation and use of the best fas­tening part for the particular function intended in our customers‘ products.

Secondly, from the moment in which our customers begin to develop a new product, our application engineering delivers the smartest solutions for all possible fastening challenges.

And thirdly, optimising our clients‘ productions in a smart and lean way with Smart Factory Logistics, our methodology, with intelligent logistics systems and tailor­made solutions.

Understood as a promise to our customers, “Proven Productivity” contains two elements: Firstly, that it demonstrably works. And secondly, that it sustainably and measurably improves the productivity and competitiveness of our customers.

And this for us is a philosophy which motivates us every day to always be one step ahead.

Bet

ter

Thro

ughp

ut

I

nnovative Technology High Quality

Time To Market Lean Process

R

elia

bilit

y

Application Engineering

Product Solutions

ProvenProductivity

Smar

t Fac

tory L

ogistics

OVERVIEW

Properties

Total overviewScrews bigger than M3

Nuts M4 to M22

Coating precote® 30 precote® 80 precote® 85Scotch-GripTM

2353

Color yellow red turquoise blue

Chemical basis Acrylate Acrylate Acrylate Epoxy resin

Temperature range

-60 to 150° C -60 to 170° C -60 to 170° C -30 to 110° C

Strength Medium High High High

Hand-tight after about

15 min 15 min 15 min No information

Functionally strong after about

6 h 6 h 6 h 6h

Final strength after

24 h 24 h 24 h 24 h

Thread friction coefficient µthrd.*

0.10 to 0.15 > 0.25 0.10 to 0.15 0.13 to 0.19

Seal up to 250 bar up to 400 bar up to 400 bar No information

Application

Particularly suited for

internal recess drive

screws and for the

electrical industry.

Very often used for its

sealing properties.

The universal type for

all threaded parts with

very high locking effect.

Suited for increased

usage temperatures

and insensitive to

humidity.

Particularly suited for

all screw connections

that are tightened with

a controlled thread

friction coefficient.

Reliable screw locking

against independent

loosening in the tem-

perature range of up to

90° C and in the short

term up to 110° C.

Shelf life 4 years at room temperature, stored dry

*All specifications related to screws M10 ISO4017-8.8, black oxide Nuts M10 ISO4017-10 black oxide Value < M10 and > M10 correspond to DIN 267-27

precote® / Scotch-GripTM 2353

The following table provides an overview of the benefits and properties of the adhesive products precote® and Scotch-GripTM 2353.

Page 11: Safeguard Against Loosening - Bossard Group

1111

PROVEN PRODUCTIVITY – A PROMISE TO OUR CUSTOMERS

The strategy for success

From years of cooperation with our customers we know what achieves proven and sustainable impact. We have identified what it takes to streng­then the competitiveness of our customers. There­fore we support our customers in three strategic core areas.

Firstly, when finding optimal product solutions, that is in the evaluation and use of the best fas­tening part for the particular function intended in our customers‘ products.

Secondly, from the moment in which our customers begin to develop a new product, our application engineering delivers the smartest solutions for all possible fastening challenges.

And thirdly, optimising our clients‘ productions in a smart and lean way with Smart Factory Logistics, our methodology, with intelligent logistics systems and tailor­made solutions.

Understood as a promise to our customers, “Proven Productivity” contains two elements: Firstly, that it demonstrably works. And secondly, that it sustainably and measurably improves the productivity and competitiveness of our customers.

And this for us is a philosophy which motivates us every day to always be one step ahead.

Bet

ter

Thro

ughp

ut

I

nnovative Technology High Quality

Time To Market Lean Process

R

elia

bilit

y

Application Engineering

Product Solutions

ProvenProductivity

Smar

t Fac

tory L

ogistics

Page 12: Safeguard Against Loosening - Bossard Group

Bossard AG Steinhauserstrasse 70P.O. BoxCH-6301 Zug

T +41 41 749 66 11 F +41 41 749 66 22

[email protected]

© B

ossa

rd A

G /

1410

_Saf

egua

rd A

gain

st L

oose

ning

/ en

/ 05

-201

8 / S

ubje

ct to

cha

nge.